Motor vehicles are customarily equipped with seat occupant detection sensors for use in connection with occupant safety systems including seat belts and pyrotechnically deployed restraints such as air bags. For example, an occupant detection sensor can be used in connection with a seat belt switch to detect an unrestrained seat occupant and trigger an appropriate reminder. Additionally, occupant detection sensors can be used to enable or disable air bag deployment for a particular seating location in the vehicle, and potentially to classify the occupant by seated weight.
A common approach to seat occupant detection involves installing one or more pressure-responsive sensors on, in, or under the bottom foam cushion of the seat. In some cases, the pressure is measured and compared to one or more calibrated thresholds, as shown for example, in the published patent application US 2006/0196281 A1. In other cases, a calibrated occupant seat pressure is detected by closure of one or more switches, as shown for example, in the published patent application US 2008/0203712 A1.